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Albert Einstein was right: There is an area at the edge of black holes where matter can no longer remain in orbit and instead falls in, as predicted by his theory of gravity.
Using telescopes capable of detecting X-rays, a team of astronomers has seen for the first time this region – known as the “immersed region” – in a black hole about 10,000 light-years from Earth. “We have ignored this region, because we didn’t have the data,” said research scientist Andrew Mummery, lead author of the study published Thursday in the journal Monthly Notices of the Royal Astronomical Society. “But now that we do, we couldn’t explain it any other way.”
This is not the first time that black holes have helped confirm Einstein’s grand theory, also known as general relativity. The first photo of a black hole, captured in 2019, reinforced the revolutionary physicist’s basic assumption that gravity is nothing more than bending the fabric of space-time.
Many of Einstein’s other predictions have proved correct over the years, including gravitational waves and the universal speed limit. “It’s a tough guy to bet against at this point,” said Mummery, a Leverhulme-Peierls Fellow in the Department of Physics at the University of Oxford in the United Kingdom.
“We went out looking for this one specifically – that was always the plan. We have debated whether we would be able to find him for a long time,” said Mummery. “People said it would be impossible, so it’s very exciting to confirm that it’s there.”
‘Like the edge of a waterfall’
The black hole has been observed in a system called MAXI J1820 + 070, which consists of a star smaller than the sun and the black hole itself, estimated at 7 to 8 solar masses. The astronomers used NASA’s NuSTAR and NICER space-based telescopes to gather data and understand how hot gas, called plasma, from the star is forced into the black hole.
NuSTAR is short for the Nuclear Spectroscopic Telescope Array, which orbits Earth, and NICER, known as the Neutron star Interior Composition Explorer, is located on the International Space Station.
“Around these black holes are large disks of orbital material (from nearby stars),” Mummery said. “Most of it is stable, which means it can flow happily. It’s like a river, but the submerged region is like the edge of a waterfall – all your support is gone and you’re just crashing your head. The biggest thing you see is the river, but there’s this tiny region at the end, and that’s basically what we got,” he said, noting that while the “river” was visible widely, this is the first evidence of the. “waterfall.”
Unlike the event horizon, which is closer to the center of the black hole and does not allow anything to escape, including light and radiation, in the “immersion region” light can still escape, but matter is doomed at the powerful gravitational pull, Mummery. explained.
The results of the study could help astronomers gain a better understanding of the formation and evolution of black holes. “We can really learn about them by studying this region, because it’s on the edge, so it gives us the most information,” Mummery said.
One thing missing from the study is an actual image of the black hole, because it is too small and far away. But another team of Oxford researchers is working on something even better than a picture: the first film of a black hole. To achieve that, the team will first need to build a new observatory, the African Millimeter Telescope in Namibia, which Mummery hopes will be online within a decade. The telescope, which will be part of the international Event Horizon Telescope collaboration that took a groundbreaking 2019 image of the black hole, will enable scientists to observe and film supermassive black holes in the center of the Milky Way galaxy and beyond.
A link to the past
According to Christopher Reynolds, a professor of astronomy at the University of Maryland, College Park, finding actual evidence for the “immersed region” is an important step that will allow scientists to significantly improve models of how matter behaves around a black hole. “For example, it can be used to measure the rotation rate of the black hole,” said Reynolds, who was not involved in the study.
Dan Wilkins, a research scientist at Stanford University in California, says it is an exciting development, and points out that in 2018 there was an extremely bright burst of light from one of the black holes within our galaxy, accompanied by a high-energy excess. . X-rays.
“We hypothesized at the time that this excess came from the hot material in the ‘plunge region,’ but we didn’t have a complete theoretical prediction of what that emission would look like,” said Wilkins, who was not involved with the organization as well. a new study.
This study actually does that calculation, he said, using Einstein’s theory of gravity to predict what X-rays emitted by matter in the “immersed region” around a black hole would look like, and compare with the data from that bright flash i. 2018.
“This will be a key area of discovery over the next decade or so,” Wilkins said, “as we look toward the next generation of X-ray telescopes that will give us more detailed measurements of the most distant regions into just outside the scope of black holes. .”
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